The use of venturi gas scrubbers is well known, as disclosed, for example, in co-owned U.S. Pat. No. 3,048,956. A stream of gas (air), contaminated with fine particulates, enters the venturi and increases markedly in linear velocity. A wash liquid (water) is injected into the accelerating gas stream to effect intimate contact between the particles and liquid droplets. The particles are thereby wetted and entrapped by the liquid droplets by the difference in velocity between the particles and the liquid droplets.
Various methods are also known for altering the cross-sectional area of the throat of a venturi-type gas scrubber in response to changes in operating conditions. In U.S. Pat. No. 3,556,489, a venturi scrubber is disclosed in which the gas velocity in the throat may be maintained at a relatively constant level, by adjusting the throat area, despite changes in inlet volumes and pressures.
One aspect of the present invention is to provide an improved means for altering the cross-sectional throat area of a venturi scrubber, such means being relatively simple in structure and operation and having the important advantages of reduced deflection, abrasion, balanced pressure, and turbulence. Specifically, it is an object to provide flow restricting means which is operable to reduce the throat area of a venturi tube without completely blocking the flow of gas, particulates, and atomized liquid through the main or central portion of the throat.
In brief, the scrubber includes a venturi tube having a throat with a substantially rectangular cross-sectional area. A rotor is mounted in the throat for rotational movement about an axis normal to the direction of gas flow. The rotor comprises a plurality of parallel members disposed in laterally spaced relation and transversely bisected by the pivot line of the rotor. In the best mode presently known for practicing the invention, each member has rounded side surfaces and preferably takes the form of a cylindrical bar.
Even when the rotor is positioned so that the bars extend across the throat, gas may flow at high velocity through the spaces between the parallel bars. Minimum obstruction and maximum cross-sectional area are produced when the rotor is turned 90 degrees to position the bars parallel with the longitudinal axis of the throat. In any selected intermediate positions (between such longitudinal and transverse positions), high velocity gas may flow about the ends of the bars as well as between such bars. Thus, since gas may flow between the bars regardless of the position of the rotor, the extent of deflection that would otherwise be produced if the rotor were solid or imperforate is avoided, the impacting of entrained particulates upon the rotor and throat surfaces is reduced, wear upon such throat surfaces and rotor is minimized, and the force of the gas stream is equal on each side of the axis, reducing the torque required for revolving the rotor.
Other advantages and objects of the invention will become apparent from the specification and drawings.